Does prophylactic photocoagulation help central retinal vein occlusion (CRVO) outcomes? This phase 3 randomized control trial in 1995 analyzed patients who had CRVO within the last year and split them into Group N (181 patients with nonperfused CRVO with no neovascularization) and Group M (151 patients with 20/50 or worse visual acuity and macular edema secondary to CRVO). The primary outcome for Group N was regression of the development of neovascularization after prophylactic pan-retinal photocoagulation (PRP). The primary outcome for Group M was visual acuity after macular grid laser therapy at 3 years.
Overall, the CVOS study is a landmark study because it did not support prophylactic photocoagulation being utilized for the treatment of CRVO. While treatment regimens have changed since the development of Anti-VEGF agents and improved clinical imaging (OCT), the CVOS remains one of the important foundational studies in the field.
- Group N: Prophylactic PRP reduced proportion of patients who developed iris or angle neovascularization, but this difference was not statistically significant (35% vs. 20%, OR 0.6, P = 0.17) after adjusting for baseline characteristics
- Group N: Iris and angle neovascularization was more successfully treated by PRP in patients who had not had prophylactic PRP (56% vs. 22%, OR 4.5, P = 0.02)
- Group M: There was no statistically significant difference in visual acuity in those who received grid laser versus those who received no treatment at 3 years.